When David Seville goes off to Europe on a business trip, the Chipmunks, Alvin, Simon and Theodore, are left at home with their babysitter, Miss Miller.

Diamond smugglers Claudia and Klaus Furschtein overhear the conversation and approach the children, telling them that they will provide them with the means for a real race around the world by hot air balloon, with the winner receiving $100,000.

However, that success presents its own trials as their unscrupulous record executive, Ian Hawke (David Cross), plans to break up this family to exploit the boys.

Pop sensations Alvin (Justin Long), Simon (Matthew Gray Gubler) and Theodore (Jesse McCartney) end up in the care of Dave Seville's (Jason Lee) twenty-something cousin Toby (Zachary Levi).

Dave (Jason Lee), the Chipmunks, and the Chipettes enjoy fun and mischief on a luxury cruise before their seafaring vacation takes an unexpected detour to an uncharted island.

Through a series of misunderstandings, Alvin (Justin Long), Simon (Matthew Gray Gubler) and Theodore (Jesse McCartney) come to believe that Dave (Jason Lee) is going to propose to his new girlfriend in Miami...and dump them.

PC (a talking laid back frog with a surfer dude accent who believes he is one kiss away from being Prince Charming) says that his mom used to say "nothing warms up a home like children's laughter".